US4747668A - Optical scanning unit - Google Patents

Optical scanning unit Download PDF

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Publication number
US4747668A
US4747668A US06/889,020 US88902086A US4747668A US 4747668 A US4747668 A US 4747668A US 88902086 A US88902086 A US 88902086A US 4747668 A US4747668 A US 4747668A
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United States
Prior art keywords
coil
magnetic body
magnetic
parts
objective
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US06/889,020
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English (en)
Inventor
Karl-Hanns Meyer
Wilhelmus A. H. Gijzen
Willy J. J. Aerts
Gerard E. van Rosmalen
Leonhard Honds
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US Philips Corp
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US Philips Corp
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Priority claimed from DE19853529091 external-priority patent/DE3529091A1/de
Priority claimed from DE19853529090 external-priority patent/DE3529090A1/de
Priority claimed from NL8503238A external-priority patent/NL8503238A/nl
Application filed by US Philips Corp filed Critical US Philips Corp
Assigned to U.S. PHILIPS CORPORATION, A CORP. OF DE. reassignment U.S. PHILIPS CORPORATION, A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: AERTS, WILLY J.J., GIJZEN, WILHELMUS A. H., MEYER, KARL-HANNS
Assigned to U.S. PHILIPS CORPORATION, A CORP. OF DE. reassignment U.S. PHILIPS CORPORATION, A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: VAN ROSMALEN, GERARD E., HONDS, LEONHARD
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0925—Electromechanical actuators for lens positioning
    • G11B7/0935—Details of the moving parts

Definitions

  • the invention relates to an optical scanning unit for the control and alignment of a beam of rays on recording tracks of an information carrier surface.
  • a scanning unit has an objective with an objective lens for focussing the radiation beam into a scanning spot on the said surface.
  • the scanning unit also has an electromagnetic drive device for continuously correcting the position of the objective with respect to the information carrier.
  • the drive device is fitted with an objective mount for the objective.
  • the objective mount has a moving, annular magnetic body of permanent-magnet material which is equipped with magnetic poles at its axial ends and which interacts magnetically through an air gap with at least three sets of fixed coils mounted in the drive. The coil sets are arranged at equal distancs from one another when seen in the peripheral direction of the magnetic body.
  • Such an optical scanning unit is known from German Pat. No. 32 34 288 which corresponds to U.S. Pat. No. 4,602,848, herewith incorporated by reference.
  • the objective is fixed in a moving, axially permanently-magnetized sleeve with two axial ends as the magnetic poles.
  • the fixed-mounted segmental coils are in the form of flat banana-shaped coils with two coil parts extending axially with respect to one another and the said sleeve. Upon excitation of the segmental coils, the current in the coil parts concerned flows in the opposite direction.
  • movements of the objective include an axial movement which is parallel to the optical axis of the objective and is used for focussing the a light beam onto an information surface of a rotating optical disc, as well as two radial movements at right angles to one another and/or two tilting movements about two axes running at right angles to one another and to the optical axis, the latter four movements being used for the radial and tangential track following of the light spot.
  • the known drive unit has the disadvantage, however, that the magnetic forces between the coils and the magnetic sleeve vary as a function of the axial displacement of the objective in such a way that even with a small axial displacement of the objective from the central position between the coil sets, the drive is no longer capable of moving the objective satisfactorily so as to achieve the necessary focussing of the light beam and the necessary track following of the light spot.
  • the widely separated coil sets are suitable, in fact, for achieving sufficient movement along the optical axis, but the possibility of producing the other movements decreases so rapidly that even at a small distance from the central position the objective is no longer adequately driven as to be able to guarantee track following of the light spot.
  • each coil set has a first segmental coil with two active coil parts at the same axial distance from the magnetic body and extending round it.
  • Each coil part is located in the vicinity of one of the axial ends of the centrally positioned magnetic body and the two coil parts are connected to one another by axially directed further coil parts.
  • the unit has at least one additional coil which is positioned at least partially between the active coil parts of the above-mentioned first segmental coil.
  • the scanning unit of the invention has the advantage that when the coils are excited, the axially and radially directed forces, which the coils exert on the magnetic body, remain almost constant when the objective is moved over a distance which is sufficient for focussing a light spot and keeping it focussed on the information surface of an optical disc.
  • a further advantage of the scanning unit of the invention is the high efficiency of the drive during axial movement of the objective. This high efficiency is the result of the favourable shape and alignment of the first segmental coils because the majority of the active parts of the first segmental coils are in regions of high magnetic field intensity.
  • the scanning unit of the invention has the further advantage that, at least in terms of its structural length, the objective mount can be small. This is important because a flat objective mount makes it possible for its center of gravity to be made to coincide with the center of gravity of the objective flange. This means that unwanted tilting of the objective can be avoided when it is being moved radially.
  • each of the above-mentioned sets has two second coils extending parallel to one another and in the form of second segmental coils. These second coils lye alongside one another when seen in the axial direction of the magnetic body, each of them having a coil part facing the magnetic body and extending in its peripheral direction and a coil part further removed from the magnetic body.
  • the above described coil configuration of the invention makes it possible to excite the second segmental coil of each set so as to move the objective in directions at right angles to the optical axis and to excite the first segmental coil of each set so as to move the objective along the optical axis.
  • the complete first segmental coils can, if desired, also be used for tilting the objective about axies at right angles to the optical axis.
  • the first segmental coils of the drive device have to be actuated for focussing a light beam into a light spot onto an information surface of an optical disc and that the second segmental coils have to be actuated for the radial and tangential track following of the light spot, where appropriate with selective actuation of the first segmental coils.
  • the coil configuration described here can be used throughout with a simple axially magnetized magnetic body.
  • each of the sets has two second coils as second segmental coils alongside one another when seen in the axial direction of the magnetic body.
  • Each of the second coils has two active coil parts at the same axial distance from the active body and extending around it.
  • One of the active parts is adjacent to the magnetic body and connected to the other active coil part by further coil parts at an angle to the magnetic body.
  • the other active coil part is located opposite the magnetic pole at one of the ends of the magnetic body.
  • the second segmental coil in this embodiment are shaped and aligned with respect to the magnetic body in such a way that by far the majority of these segmental coils lie in favourable regions of the magnetic field of the magnetic body. This means that a high efficiency can be obtained with smaller diametric dimensions of the drive device in the case of both axial and radial driving.
  • each of the sets contains a second, annular coil extending in a radial plane about the magnetic body.
  • the coil parts positioned at the outside in the present state of the art which are now arranged at the same distance from the magnetic body as the coil parts which were previously only on the inside and were active, are now also active with respect to the control system. This is based on the fact that in the case of a multi-part permanent-magnetic body, in which the magnetic parts are magnetized differently, there are magnetic field areas in which both the previously active parts on the inside and the outside non-active parts at the present state of the art can now also be active. Because the coil parts previously at the outside are now brought closer to the magnetic body, the diameter of the device becomes smaller and space is made available for other components.
  • the annular coil in the central radial plane produces essentially axial actuating forces for focus adjustment of the magnetic body.
  • the coil preferably produces radial actuating forces which act on the magnetic body. Thanks to this subdivision of coils it is possible to employ the actuating forces more systematically during the excitation of the coils.
  • An optical scanning unit constructed in this way acts as a three-axis actuator with three components of motion at right angles to one another. This considerably simplifies the coil system while retaining the preferred actuating forces in the radial and axial directions.
  • the optical scanning unit for the control and alignment of a beam of rays on recording tracks of a surface being scanned has an objective with an optical axis which is equipped with an objective lens for focussing the beam of rays into a scanning spot on the said surface, and, in addition, has an electromagnetic drive device for the continuous correction of the position of the objective with respect to the information carrier, wherein the drive device is equipped with an objective mounting for the objective, this objective mounting has a moving ring-shaped body arranged coaxially with the optical axis, which is equipped at the ends with magnetic poles and consists of permanent-magnetic parts superimposed axially one on the other and wherein the drive device is further equipped with fixed coils which interact magnetically with the said magnetic body via an air gap and which contain at least three segmental coil sets each with two segmental coils, these sets being arranged at equal distances alongside one another when seen in the peripheral direction of the magnetic body, the optical scanning unit is characterized by the fact that each individual segmental coil has two active coil
  • an annular coil located between the said segmental coils of the coil sets, extends in a circle around the centre of the magnetic body in a radial plane.
  • the toroidal coil makes it possible to amplify the axial actuating components.
  • all the segmental coils of the segmental coil sets and the annular coil consist of laminar conductors which are provided on a cylindrical carrier which encloses the magnetic body.
  • the coils can be made extraordinarily flat and build on a cylindrical shell.
  • the manufacture of the coil sets is easy to perform technically and is ideally suited to mass production.
  • an intermediate part which is non-magnetic, soft-magnetic or also permanent-magnetic, is arranged between the permanent-magnetic parts of the magnetic body.
  • the intermediate part is non-magnetic, the dynamic effects in the radial and axial directions can be separated more effectively. If the intermediate part is ferromagnetic, then the radial component can be amplified. If the intermediate part is permanent-magnetic, then the radial component can be amplified even further. Alltogether this means that by inserting the intermediate part it is possible to obtain properties of the system (magnet/coil configuration) which cannot be achieved without it.
  • the parts of the magnetic body are permanently magnetized in opposing directions. This form of magnetization is the easiest to achieve technically.
  • the north poles of the parts of the magnetic body are oriented in the direction of the intermediate part and the north poles of the intermediate part are oriented towards its outside wall. Conversely, it is equally possible to reverse the north pole orientation so that the north poles of the parts are oriented towards the axial ends and the north poles of the intermediate part towards its inside wall.
  • FIG. 1 is a schematic representation of part of the scanning unit of the invention
  • FIG. 2 is an exploded view of a first embodiment of the drive according to the invention
  • FIG. 3 is a top view of the drive illustrated in FIG. 2,
  • FIG. 4 is a section along the line IV--IV in FIG. 3,
  • FIG. 5 is an exploded view of a second embodiment of the drive of the scanning unit according to the invention.
  • FIG. 6 is a longitudinal section through the drive shown in FIG. 5.
  • FIG. 7 a section through an optical scanning unit with a two-part permanent-magnetic magnetic body which supports the objective, with coil sets, arranged outside the magnetic body, in the area of the axial ends, and with an annular coil in the area of the radial central plane located between the coil sets.
  • FIG. 8 is a simplified diagrammatic representation of the embodiment shown in FIG. 7,
  • FIG. 9 is a modified version of the embodiment in FIG. 7, in which only one coil set is used, the coil parts running in the peripheral direction are arranged, on the one hand, in the area of one axial end of the magnetic body and, on the other, in the area of the other axial end, where, once again, the annular coil is located in the radial central plane between the coil parts situated at the ends,
  • FIG. 10 is a simplified diagrammatic representation of the optical unit in FIG. 9,
  • FIG. 11 is a magnetic body consisting of several magnetic parts
  • FIG. 12 is a representation of a segmental coil of the coil set in FIG. 10 with the driving forces emanating from this segmental coil
  • FIG. 13 is a section through a modified optical scanning unit with the coils and the magnetic fields of the magnetic body
  • FIG. 14 is a modification of the two-part magnetic body with an intermediate part between the two magnetic parts
  • FIG. 15 is a diagrammatic representation of the construction of the coil sets as shown in FIG. 13 and of the magnetic body arranged in the coil sets,
  • FIG. 16 is a segmental coil of a coil set as shown in FIG. 10 with the dynamic effect originating from it,
  • FIG. 17 shows a three part magnetic body.
  • the scanning unit shown in FIG. 1 has a radiation source 1, for example a diode laser, a collimator lens 3 and an objective 5 with an optical axis 5A.
  • the objective is arranged in an objective mount 7 of an electromagnetic drive which will be described in detail subsequently.
  • the collimator lens 3 and the objective 5 can have several lens elements, but consist preferably of a single lens element with at least one aspherically refracting surface.
  • the objective comprises only one objective lens which was produced by a replica method, the objective lens being equipped with a ring-shaped mirror 9 for a position detection system not described in detail here.
  • Such a position detection system is described in Dutch Pat. No. 8501665 which corresponds to U.S. Pat. No. 4,638,471 herewith incorporated by reference.
  • the divergent beam of rays b supplied by the radiation source 1 is converted by the collimator lens 3 into a parallel beam which fills the aperture of the objective 5 perfectly.
  • the objective focusses the beam of rays into a diffraction-limited radiation spot V with a diameter of, for example, 1 ⁇ m on the information surface 11 of a disc-shaped information carrier 13 of which a small part is shown in radial section in FIG. 1.
  • the information is arranged in centric tracks 15 or quasi-concentric tracks which form a spiral track.
  • the information consists of a plurality of optically detectable information regions between which there are intermediate regions.
  • the information surface 11 is close to the top of the information carrier 13 so that the beam b passes through the transparent substrate 17 of the information carrier before it reaches the information surface.
  • the information surface is, preferably, radiation-reflecting so that the beam is reflected in the direction of the radiation source.
  • the beam reflected from the information surface is modulated in accordance with the sequence of information regions and intermediate regions in the track being read.
  • the modulated beam is separated from the beam emitted from the radiation source, by an uncoupling element 19 in the form, for example, of a part prism.
  • the separating plane 21 of the prism reflects at least part of the reflected beam to the radiation-sensitive detector 23 positioned in the radiation path.
  • the detector 23 converts the modulated beam into an electrical signal which, in the known manner, is processed into a signal which, depending on the form of the information stored in the information carrier, can be made visible or audible or processed in another way.
  • FIG. 1 On the righthand side of FIG. 1 there is drawn an orthogonal coordinate system XYZ which must be considered to have its origin O at the point M so that the z-axis coincides with the principal ray L of the beam b.
  • the Z-axis extends in the axial direction, and this is the direction in which the objective must be able to be moved in order to focus the beam b in the light spot V.
  • the X-axis and the Y-axis extend in the radial and tangential directions, respectively, with respect to axis of rotation of the information carrier.
  • the objective 5 Because the light spot V has to follow the tracks of the rotating information disc as closely as possible, it is necessary for the objective 5 to make straight-line movements along the X-axis and the Y-axis, as well as rotate about these axes.
  • the movement of the objective along the Z-axis is also known as the focussing movement, while the other movements are also known as the track following and time-error correcting movements.
  • FIGS. 2 to 6 illustrate in detail several possible electromagnetic drives for the scanning unit of the invention.
  • each drive comprises a flexibly suspended ring-shaped magnetic body and a number of fixed coils arranged around this body, the coils being arranged into three or four sets.
  • the magnetic body is ring-shaped or sleeve-shaped and is made from a permanent-magnet material.
  • the coils in the sets are located in specific parts of the magnetic force field of the magnetic body.
  • the objective is magnetically mounted in the drive device so that there is no physical contact between the objective and the objective mount, on the one hand, and the remaining elements of the scanning unit on the other hand.
  • FIGS. 2, 3 and 4 show a drive with a magnetic body 200 which is axially magnetized, as indicated by arrows in FIG. 4, so that a south pole Z or a north pole N are formed at the axial ends of the magnetic body 200.
  • Magnetic materials with a high energy content such as neodymium-iron-boron and samarium-cobalt are preferred.
  • the magnetic body 200 and a holding ring 202 form the objective mount 7 for the objective 5.
  • the coils are subdivided in this embodiment into three sets which are designated as 204, 205 and 206.
  • the sets 204, 205 and 206 are arranged uniformally about the magnetic body 200, i.e. adjacent to one another, as seen in the peripheral direction of the magnetic body 200, and together form a more or less closed shell around the magnetic body 200.
  • three sets it is also possible to arrange the coils into four or more than four sets in the manner illustrated.
  • Each of the sets 204, 205 and 206 has a first segemental coil 204A, 205A or 206A respectively which is shaped and arranged in such a way that two active coil parts 204A1, 205A1 or 206A1 of the three segmental coils are located close to the magnetic body and, in fact, in regions where the magnetic field lines are directed mainly radially.
  • segmental coils 204, 205, 206 When segmental coils 204, 205, 206 are excited, they can therefore exert magnetic force, produced along the Z-axis, on the magnetic body so that the objective 5 is moved for focussing purposes, out of the central position shown in FIG. 4.
  • the above-mentioned active coil parts are connected to one another in pairs by inactive coil parts 204A2, 205A2 or 206A2 respectively.
  • Each of the sets 204, 205 and 206 is further provided with two second segmental coils 204B, 205B and 206B which extend parallel to one another. These segmental coils are banana-shaped and are arranged more or less in the above-mentioned first segmental coils 204A, 205A and 206A, respectively.
  • the second segmental coils 204B, 205B and 206B each have an active coil part 204B1, 205B1 and 206B1 facing the magnetic body 200 and located in a part of the magnetic field of the magnetic body 200 where the field lines run mainly axially.
  • the second segmental coils can exert mainly radially directed magnetic forces on the magnetic body 200 which in the case of certain combinations of excited coils form turning moments. From what has been said above, it is probably clear that be selective actuation of the second magnetic coils 204B, 205B and 206B the objective 5 is moved along the X-axis and the Y-axis and can be tilted about the X-axis and the Y-axis for the purpose of track following and time correction, as already mentioned, when a rotating optical disc is being read.
  • the electromagnetic drive illustrated in FIGS. 5 and 6 is largely the same as the drive described above and is therefore only described briefly.
  • the drive has a magnetic body 200, in which the mount 202 with the objective 5 is secured.
  • the drive also has three sets of magnetic coils 504, 505 and 506 which are arranged around the magnetic body 200 in the manner already described.
  • a frame is required, and the supporting plate 208 of this frame is represented schematically.
  • Each of the sets 504, 505 and 506 is comprised of three segmental coils, namely a first segmental coild 504A, 505A and 506A respectively and two second segmental coils 504B, 505B and 506B respectively.
  • the first segmental coils 504A, 505A and 506A are the same as the first segmental coils 204A, 205A and 206A of the embodiment described above and are not described in any further detail.
  • the two second segmental coils 504B, 505B and 506B of each of the sets 504, 505 and 506 are in tandem when viewed in the focussing direction.
  • Each of the segmental coils 504B, 505B and 506B are more or less wing-shaped or curved and have two active coil parts 504B1, 505B1 and 506B1 each of which is positioned in a region of the magnetic field of the magnetic body 200 where the field lines extend mainly parallel to the Z-axis.
  • the shape and alignment of the second segmental coils 504B, 505B and 506B enable rapid and very precisely defined track following and time correction movements of the objective, namely be straight-line movement along and rotation about the X- and Y-axes of the magnetic body 200.
  • the tilting movements of the objective about the said X- and Y-axes can be achieved by actuation of the first segmental coils, by actuation of second segmental coils or by combined actuation of first and second segmental coils in the illustrated embodiments.
  • an objective 601 is arranged in a permanent-magnetic body 603.
  • This magnetic body has two magnetic parts 603a and 603b. Both parts 603a and 603b are axially magnetized in the opposite direction, as indicated by the arrows 605b and 605a. As a result of the magnetization illustrated by arrows 605a and 605b, a magnetic field indicated by the magnetic field lines 607 is formed outside the magnetic body 603.
  • Coil sets 613 and 615 are arranged around the magnetic body 603 in the region of its axial ends 609, 611.
  • a toroidal coil 619 is arranged around body 603 in the area of the connecting surface 617 between the magnetic parts 603a and 603b.
  • the construction of the overall coil arrangement is illustrated disgrammatically in FIG. 8. For the purpose of illustration, the coil construction as a whole has been considerably enlarged. In a practical version, the coil arrangement and axial sleeve length are only a few millimeters high.
  • Coil sets 613 and 615 are the same in design and construction.
  • Each of the coil sets 615, 613 has several segmental coils 615.1, 615.2, 615.3, 615,4 or 613.1, 613.2, 613.3, 613.5, respectively.
  • the individual segmental coils are in the form of sections of a cylindrical shell which fit together in the peripheral direction of the cylinder to form a cylindrical shell.
  • each individual segmental coil 613.1 to 615.4 comprises two arc-shaped coil parts 613a, 613b and 615a, 615b respectively.
  • the respective coil parts 613a and 615a together form a composite upper coil ring, whereas all the coil sections 613b or 615b jointly form a lower composite coil ring.
  • All the coil parts 613a, 613b and 615a, 615b have the same curvature and all are approximately the same distance away from the central axis 621.
  • the coil parts 613a and 613b and 615a and 615b are connected to one another by connecting links 613c and 613d and 615c and 615d.
  • These connecting links run in the direction of or parallel to the axis 621.
  • the connecting links 613c, 613d and 615c, 615d are of practically no significance for the control system, whereas coil parts 613a and 613b, 615a and 615b jointly contribute towards the control of the position of the magnetic body 603 within the coil arrangement.
  • FIGS. 9 and 10 show a simplified scanning unit in which only one segmental coil set 715 is provided.
  • the magnetic body 603 once again has two magnetic parts 603a and 603b which are axially magnetized at the axial ends 609 and 611 in the direction of the arrows 605a and 605b.
  • the two magnetic parts 603a and 603b are joined to one another along a surface 617.
  • the lens 601 is arranged within the inside 623 of the body 603. Again, the magnetic fields of the magnetic body 603 produce the magnetic field lines 607.
  • the set of segmental coils 715 is arranged around the magnetic body 603 and coaxially to it.
  • Segmental coil set 715 comprises, for example, four segmental coils 715.1, 715.2, 715.3 and 715.4.
  • the individual segmental coils form sections of a cylindrical shell and join together in the peripheral direction of the cylinder to form a cylindrical shell. This cylindrical shell encloses the magnetic body 603.
  • Each individual segmental coil 715.1 to 715.4 has two coil parts 715a and 715b. Both the coil parts 715a and the coil parts 715b join together in the region of the upper end 611 or the lower end 609 to form composite coil rings which enclose ends 611 and 609 with some clearance.
  • the coil parts 715a and 715b all have the same curvature and approximately the same clearance from the central axis 621.
  • the coil parts 715a and 715b of segmental coils 715.1 to 715.4 are connected at their ends by connecting links 715c and 715d. These connecting links 715c and 715d run parallel to the axis 621 and therefore in the axial direction.
  • the toroidal coil 619 is provided between coil parts 715a and 715b.
  • the toroidal coil and the individual segmental coils can be actuated separately by an electronic control unit. Whereas the toroidal coil 619 effects adjustment only in the axial direction, i.e. in the Z direction, coil parts 715a and 715b can also effect adjustments in the direction of the X and Y coordinate axes, depending on how they are actuated.
  • the magnetic body 200 may be formed by three superposed rings 250, 251 and 252.
  • the two outer parts or rings 250 and 252 are magnetic and are magnetized in the axial direction.
  • the intermediate ring or part 251 in this embodiment is non-magnetic.
  • the objective 601 is mounted within the assembly formed by the three annular parts 250, 251 and 252.
  • FIG. 11 shows a magnetic body 703 which has three magnetic parts 703a, 703b and 703c.
  • the magnetic parts 703a and 703b are permanently magnetized in opposite directions. This is indicated by the magnetization arrows 605a and 605b.
  • the intermediate part 703c is permanent-magnetic and is magnetized in the direction of the inside wall 623. This is represented by arrow 625.
  • the north poles of parts 703a and 703b are located in the area of the axial ends 609 and 611, while the north poles of the intermediate part 703c are situated towards the inside wall 623.
  • a coil arrangement is used like that which was described in reference with FIGS. 9 and 10. Consequently, there are only segmental coils 715.1 to 715.4 (only 715.1 and 715.3 being shown in FIG. 11) coils parts 715a and 715b being located in the area of the axial ends 609 and 611.
  • FIG. 12 illustrates, using several arrows 629, the effect of forces, originating from the individual coil parts 715a and 715b and the connecting links 615c and 615d, when a current flows in the direction of arrow 627.
  • the effects of connecting links 615c and 615d clearly cancel each other. This means that the effects of the forces from the connecting links running parallel to the central axis can make neither a positive nor a negative contribution to the control of the magnetic body. Things are different in the case of coil parts 615a and 615b.
  • the arrows originating from these coil parts show that, when current is flowing in the direction indicated by the arrow 627, the actions of the forces of these coil parts are outwards.
  • FIG. 9 contains force arrows 631 and 633 indicating the direction of force from the individual coil parts.
  • the +b arrows in FIG. 9 indicate the direction of flux of the field lines.
  • the coils 613.1 to 613.4; 615.1 to 615.4; 715.1 to 715.4 and 619 of the optical unit can be mounted as laminar conductors on an insulating cylinder 635 made, for example, from resin-bonded paper etc.
  • Such a construction, as indicated in FIGS. 8 and 10, is simple and suitable for mass production.
  • the objective 801 indicated by a dash line in FIG. 13 is arranged on the inside 802 of a permanent-magnetic body 803.
  • the magnetic body consists of two magnetic parts 803a and 803b which are secured to one another, by adhesive for example, along a surface 804.
  • the magnetic field which forms around the magnetic body 803 is indicated by the magnetic field lines 807. Because of the magnetization in opposite directions the north poles of the magnetic parts 803a and 803b are in the region of the axial ends 809 and 811.
  • segmental coil sets 813 and 815 are arranged around the magnetic body 803 at a distance permitting free movement of the magnetic body 803.
  • the segmental coil set 813 and the segmental coil set 815 roughly surround the axial ends 809 and 811.
  • the magnetic body 903 may also comprise two magnetic parts 903a and 903b between which there is an intermediate part 903c.
  • the magnetization is selected in such a way that, like the magnetization in FIG. 13, the magnetic parts 903a and 903b are magnetized in the direction of the axial ends 809 and 811.
  • the intermediate part in this case is magnetized in the direction of its inside wall 817.
  • These directions of magnetization mean that the north poles of magnetic parts 903a and 903b are at the axial ends 809 and 811 and the north poles of the intermediate part 903c are at the inside wall 817 of the intermediate part.
  • the arrangement of the segmental coil sets 813 and 815 is the same as the arrangement of these segmental coil sets in FIG. 13.
  • FIG. 15 shows the coil arrangement surrounding the magnetic body 803.
  • the magnetic body 803 is indicated only by its magnetic parts 803a and 803b and by its axial ends 809 and 811.
  • the segmental coil sets 813 and 815 each consist of four segmental coils.
  • the segmental coil set 813 comprises the segmental coils 813.1, 813.2, 813.3, 813.4.
  • the segmental coil set 815 comprises the four segmental coils 815.1, 815.2, 815.3, 815.4.
  • Each segmental coil 813.1 to 815.4 is designed as a section of a cylindrical shell. All the segmental coils 813.1 to 813.4 and 815.1 to 815.4 when combined form two cylindrical shells which surround the magnetic body 803, axially offset with respect to one another.
  • Each individual segmental coil 813.1 to 813.4 or 815.1 to 815.4 comprises similarly curved and axially offset coil parts 813a and 813b and 815a and 815b respectively. All the coil parts 813a, 813b and 815a, 815b of all segmental coils 813.1 to 815.4 are equidistant from the central axis 821 and all, therefore, have a controlling effect on the magnetic body 803.
  • the coil parts 813a and 813b as well as 815a and 815b of all individual coils are connected to one another via connecting links 813c and 813d or 815c and 815d respectively.
  • These connecting links 813c and 813d or 815c and 815d run parallel to the axis 821.
  • the connecting links of adjacent segmental coils are directly next to one another. As will be explained later, these connecting links have scarcely any influence on the control or adjustment of the magnetic body 803.
  • FIG. 16 shows a schematic diagram of a segmental coil 813.1 which is representative of all the segmental coils 813.1 to 815.4.
  • these segmental coils have coil parts 813a and 813b curved about the axis 821 which are connected to one another by connecting links 813c and 813d.
  • the field forces of the connecting links 813c and 813d run separately in the peripheral direction.
  • the pattern of forces reveals that the actions of the forces of the connecting links 813a and 813d cancel each other around the individual segmental coils and are therefore ineffective.
  • the actions of the forces of coil parts 813a and 813b can be utilized to exert controlling influence on the magnetic body.
  • FIG. 13 depicts field forces originating from one of the segmental coils of the segmental coil set. From this it is possible to derive the field forces exerted on the magnetic body 803.
  • the +b arrows indicate the pattern of the field flux along the field line.
  • the construction of the coil arrangement of the optical unit is particularly suitable for mass production if all the coils 813.1 to 815.4 are mounted, for example, in the form of laminar conductors on to the surface 829 of an insulating cylinder 831 of resin-bonded paper, for example, etc. as indicated in FIG. 15.
US06/889,020 1985-08-14 1986-07-24 Optical scanning unit Expired - Fee Related US4747668A (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
DE19853529091 DE3529091A1 (de) 1985-08-14 1985-08-14 Lichtoptische vorrichtung zur lenkung bzw. ausrichtung eines strahlenbuendels
DE3529091 1985-08-14
DE3529090 1985-08-14
DE19853529090 DE3529090A1 (de) 1985-08-14 1985-08-14 Lichtoptische vorrichtung zur lenkung bzw. ausrichtung eines strahlenbuendels auf spuren eines informationstraegers
NL8503238A NL8503238A (nl) 1985-11-25 1985-11-25 Optische aftasteenheid.
NL8503238 1985-11-25

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US4747668A true US4747668A (en) 1988-05-31

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US06/889,020 Expired - Fee Related US4747668A (en) 1985-08-14 1986-07-24 Optical scanning unit

Country Status (6)

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US (1) US4747668A (de)
EP (2) EP0334392B1 (de)
JP (1) JP2598394B2 (de)
KR (1) KR940008403B1 (de)
CA (1) CA1262963A (de)
DE (2) DE3687840D1 (de)

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Publication number Priority date Publication date Assignee Title
US4984226A (en) * 1986-07-28 1991-01-08 Kabushiki Kaisha Toshiba Magnetoptic head for recording/erasing information using a cylindrical hollow permanent magnet
US5107372A (en) * 1989-09-06 1992-04-21 Daniel Gelbart Focus servo actuator for moving lens scanners
US20030178901A1 (en) * 2002-03-25 2003-09-25 Clarity, Llc Electromagnetic positioning
US6803738B2 (en) * 2000-10-13 2004-10-12 Clarity, Llc Magnetic actuation and positioning
US20050077797A1 (en) * 2003-02-14 2005-04-14 American Superconductor Corporation Rotor assembly
US7009321B1 (en) * 2004-10-04 2006-03-07 L-3 Communications Sonoma Eo, Inc. Compact two-axis wide gap torquer motor

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US4421997A (en) * 1978-09-18 1983-12-20 Mcdonnell Douglas Corporation Multiple axis actuator
US4510421A (en) * 1982-07-10 1985-04-09 Krauss-Maffei Aktiengesellschaft Linear magnet
JPS60162472A (ja) * 1984-01-31 1985-08-24 Yoshiteru Takahashi 効率良好な直流リニアモ−タ
US4602848A (en) * 1982-09-16 1986-07-29 U.S. Philips Corporation Optical apparatus with 5-degree of-freedom positioning device
US4643522A (en) * 1983-08-03 1987-02-17 Sony Corporation Optical pickup having a driving unit for moving objective lens

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FR2443734A1 (fr) * 1978-12-08 1980-07-04 Thomson Csf Dispositif d'acces a une piste portee par un support enregistrable ou lisible optiquement et systeme optique comportant un tel dispositif
NL8103305A (nl) * 1981-07-10 1983-02-01 Philips Nv Opto-elektronische inrichting voor het met een stralingsbundel inschrijven en/of uitlezen van registratiesporen.
US4574369A (en) * 1982-01-28 1986-03-04 Ricoh Co., Ltd. Tracking/focusing device for positioning an optical lens unit
NL8303700A (nl) * 1983-10-27 1985-05-17 Philips Nv Electro-optische inrichting.
NL8403052A (nl) * 1984-10-08 1986-05-01 Philips Nv Optische inrichting.

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Publication number Priority date Publication date Assignee Title
US4421997A (en) * 1978-09-18 1983-12-20 Mcdonnell Douglas Corporation Multiple axis actuator
US4510421A (en) * 1982-07-10 1985-04-09 Krauss-Maffei Aktiengesellschaft Linear magnet
US4602848A (en) * 1982-09-16 1986-07-29 U.S. Philips Corporation Optical apparatus with 5-degree of-freedom positioning device
US4643522A (en) * 1983-08-03 1987-02-17 Sony Corporation Optical pickup having a driving unit for moving objective lens
JPS60162472A (ja) * 1984-01-31 1985-08-24 Yoshiteru Takahashi 効率良好な直流リニアモ−タ

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4984226A (en) * 1986-07-28 1991-01-08 Kabushiki Kaisha Toshiba Magnetoptic head for recording/erasing information using a cylindrical hollow permanent magnet
US5107372A (en) * 1989-09-06 1992-04-21 Daniel Gelbart Focus servo actuator for moving lens scanners
US6803738B2 (en) * 2000-10-13 2004-10-12 Clarity, Llc Magnetic actuation and positioning
US20030178901A1 (en) * 2002-03-25 2003-09-25 Clarity, Llc Electromagnetic positioning
US6879082B2 (en) 2002-03-25 2005-04-12 Clarity Technologies, Inc. Electromagnetic positioning
US20050077797A1 (en) * 2003-02-14 2005-04-14 American Superconductor Corporation Rotor assembly
US7009321B1 (en) * 2004-10-04 2006-03-07 L-3 Communications Sonoma Eo, Inc. Compact two-axis wide gap torquer motor

Also Published As

Publication number Publication date
DE3687840D1 (de) 1993-04-01
EP0214677B1 (de) 1992-01-02
KR940008403B1 (ko) 1994-09-14
CA1262963A (en) 1989-11-14
KR870002458A (ko) 1987-03-31
EP0334392B1 (de) 1993-02-24
EP0334392A1 (de) 1989-09-27
JPS6254844A (ja) 1987-03-10
EP0214677A1 (de) 1987-03-18
JP2598394B2 (ja) 1997-04-09
DE3683221D1 (de) 1992-02-13

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